Chair base



FIG. 1 is a perspective view of chair base according to the present invention;

FIG. 2 is a front view of a chair base according to the present invention;

FIG. 3 is a rear view of a chair base according to the present invention;

FIG. 4 is a left side elevation view of a chair base according to the present invention;

FIG. 5 is a right side elevation view of chair base according to the present invention;

FIG. 6 is a top view of a chair base according to the present invention; and,

FIG. 7 is a bottom view of a chair base according to the present invention.

The broken lines shown in the drawings depict portions of the chair base that form no part of the claimed design. 

CLAIM The ornamental design for a chair base, as shown and described. 